Viscosity which fluctuates as a function of temperature is one of the main problems in the flow measurement and monitoring of oils or other viscous media. Inexpensive units e.G. On the float principle, have up to now either had to be calibrated to a constant viscosity figure [which can seldom be guaranteed] or a relatively large error accepted [e.G. 2500 % if the viscosity rises from 1 to 760 cst and a flow rate of 0.1 per l/min].
Units with partial viscosity compensation, with spring-loaded floats, still show an error of around 500% for the viscosity change and flow rate mentioned. If it was required to measure precisely in spite of fluctuating viscosities then units on the displacement principle to [e.G. Oval wheel meters] would have to be used, which though they are very precise, are also expensive.
Our viscosity compensated flow and monitoring units work on the float principle with a measuring accuracy of 5% of the full-scale value for a viscosity change from 1 to 540 cst.
These type vkg units are fitted with a spring-loaded float, which in turn is guided in a cylindrical glass measuring tube and unlike previously known systems fitted with an orifice. Due to this and other design measures we have succeeded for the first time in designing a low cost flow meter and monitor, which above all exhibits a complete viscosity and advanced density compensation even at the smallest flow rates. The installed position is optional, and possible without re-calibration of the scale. The instantaneous flow figures can be read off directly from the position of the float on the scale on the glass measuring tube, which at the same time allows a check [e.G. The colour] on the medium. For dark-coloured media, for which it is known to be difficult, a magnetically coupled pointer indicator can also be supplied. For the simultaneous monitoring of the flow, up to 2 volt-free bistable reed contacts can be used.
The measurement and switching range lies between 0.1 and 80 l/min. The connection to the inlet and outlet of the units is through an internal pipe thread. The parts wetted by the medium are manufactured as standard in brass, or for aggressive media in stainless steel. The wide range of accessories for these units include various flow measurement converters also with display and/or contacts, stainless steel needle valves, block adjustment valves in a building block system for up to 8 flow measurement units and dirt traps with magnetic separators.
